A VARIABLE is a quantity that may change within the context of a mathematical problem or experiment. Typically, we use a single letter to represent a variable. The letters x, y, and z are common generic symbols used for variables.
Acceleration, rate at which velocity changes with time, in terms of both speed and direction. A POINT or an object moving in a straight line is accelerated if it SPEEDS up or slows down. ... Acceleration is defined as the change in the velocity vector in a time interval, divided by the time interval.